Cross-Laminated Timber, or CLT, is a massive structural composite panel product usually consisting of 3 to 9 layers of dimensional timber (lamellas) arranged perpendicular to each other, much like layers of veneer in plywood, and can be used as prefabricated wall, floor and roofing elements in residential, public, and commercial structures. This is not merely a new engineered composite product ("plywood on steroids") but an entirely new building technology revolutionizing the use of timber in construction. The CLT manufacturing and the technology of erecting prefabricated houses based on this product has been developed in Europe over the last 20 years despite lack of a product standard. The novel aspects of this technology has reignited interest in many aspects of composites theory, heat and mass transfer, integrity and long term performance of adhesive bonds, building physics that have been deemed secondary or not important for many traditional wood-based materials. Quite often the simplified analytical tools used with other materials are not sufficient.
For a broader perspective, see College of Forestry website on CLT which mentions President's Ray January 2015 address on CLT.